The present invention relates to magneto-optic chips and displays and, more particularly, to methods of constructing and operating such magneto-optic chips to effect gray-scale operation thereof with a broad dynamic range.
Magneto-optic chips are rapidly gaining popularity in the display art. A typical chip is shown in simplified form in FIG. 1. The chip, generally indicated as 10, comprises a substrate 12 having an appropriate film 14 on its surface. The film is of a material such as garnate which can impose the Faraday effect on polarized light passing therethrough. The film 14 is divided into individual pixel areas or posts 16. Typically, the posts 16 are laid out in a rectangular pattern of columns and rows such as those labelled for convenience C1-C6 (for column 1 through column 6) and R1-R6 (for row 1 through row 6), respectively. A series of row control wires 18 and column control wires 20 are disposed between the posts 16 as shown in FIG. 1. A more detailed explanation of the method of constructing such chips and their operation can be acquired by reference to co-pending applications Ser. No. 321,149, now U.S. Pat. No. 4,563,236 granted on 1-7-86, 503,404, now U.S. Pat. No. 4,578,321 granted on 3-25-86, and 523,011, now U.S. Pat. No. 4,550,389, granted on 10-29-85, which are also assigned to the assignee of the present invention. For convenience, the row control wires 18 are labelled as CR1-CR6 (for control row) while the column control wires 20 are similarly labelled CC1-CC6 (for control column). The single post (pixel) 16 for column 1, row 1 (C1, R1) is shown greatly enlarged in FIG. 2. By control of the current direction in CR1 and CC1, the film 14 of the post 16 of FIG. 2 can be magnetized into the post 16 as FIG. 2 is viewed or magnetized out of the post 16 of FIG. 2 as it is viewed. Such simple operation provides only two levels of brightness for each pixel position. Such basic, bi-stable operation of each pixel position is insufficient to do more than basic displays of information which are directly readable or projectible. The application of such chips to more exotic uses such as spatial filtering is prevented by their inability to assume varying stages of brightness to, thereby, afford such magneto-optic chips with a broad dynamic range.
Wherefore, it is the object of the present invention to provide methods of contruction and operation of magneto-optic chips so as to effect broad dynamic range in such devices.